In order to improve run-flat performance such as runable distance of a pneumatic tire, as shown in FIG. 4, a tire which has a sidewall portion (s) reinforced with a relatively thick rubber layer (g) has been proposed, wherein this thick rubber layer (g) is disposed on the axially inside of the carcass to extend along the inside of the tire.
In this reinforcing structure, however, under run-flat conditions, damage starting from a carcass ply turnup edge (f1) is liable to occur when the edge (f1) is positioned in the sidewall portion, especially it is positioned around the maximum tire section width point. Further, the rubber layer (g) has a maximum thickness at the maximum tire section width point. Under flat conditions, however, bending deformation becomes larger in the tire shoulder portion than the maximum tire section width portion. In other words, the bending deformation concentrates on the shoulder portion. Thus, in this structure, the tire has a tendency to have a week point in the shoulder portion.
Such drawbacks may be eliminated by for example covering the edge (f1) with an additional carcass ply and increasing the thickness of the rubber layer (g). However, other problems such as an increase in the tire weight and deterioration of ride comfort and dynamic performance under normal conditions, arise.